Historical perspectives of occupational cancer.

Three topics are discussed in this review, which is not intended to give even a short description of the history of occupational cancer. First, the present state and possible future trends of occupational cancer are examined. Such factors as rapid industrialization, increasing amounts of chemical compounds in the environment, and discoveries of new occupational carcinogens such as asbestos and vinyl chloride indicate that occupational cancer is likely to become more frequent in the future. The controversial issue of the proportion of cancers related to occupation is briefly considered. The upward trend of estimates of various authors during a quarter of a century indicates a growing proportion of occupational cancers in the overall incidence of cancer. Second, some lessons from the past are considered. Careful observations and alertness of physicians and proper documentation of occupational cancer cases are pointed out. Interdisciplinary teamwork and international cooperation have been useful in the past and continue to be desirable. Some details of the studies of skin cancer caused by mineral oil are informative. Individual susceptibility, whether genetically determined or due to pathological conditions, needs further study. As an example of the predictive value of animal experiments, skin cancer related to the oil shale industry in Estonia is discussed. The third topic--input from experimental cancer research--deals mainly with the problem of modifying factors. Experimental data on such factors could facilitate investigations of life-style effects, using the proposed classification of modifying factors. The problem of nasal cancer in woodworkers may be easier to solve by taking into account some experimental data on tannin-containing material. Some possibilities for future action and suggestions for further research are outlined.